1. Field of the Invention
The present invention relates to a piezoelectric actuator, a method of manufacturing a piezoelectric actuator, and a liquid ejection head, and more particularly to technology for raising piezoelectric properties.
2. Description of the Related Art
Piezoelectric actuators using piezoelectric elements have been developed. It has been reported that, in a piezoelectric actuator of this kind, since a film of piezoelectric material (piezoelectric film) is formed directly on top of a substrate, the displacement of the piezoelectric film in the direction along the film surface is constrained (in the following description, this is also called “substrate constraint”) and the piezoelectric properties decline accordingly (see “Piezoelectric Properties of Ferroelectric Epitaxial Films with High Curie temperature” by Takeshi Yoshimura and Susan Trolier-McKinstry, IEEJ (Institute of Electrical Engineers of Japan) Transactions on Sensors and Micromachines, April 2004 Volume 124-E Number 4, pp. 117-123). This paper discloses technology in which, by using a film having high piezoelectric properties due to epitaxial growth of the piezoelectric elements, decline in the piezoelectric properties caused by the substrate constraint, or the like, is counteracted. Although this paper discloses technology which raises the piezoelectric properties of the piezoelectric film itself, it does not disclose technology which reduces the effects of the substrate constraint on the piezoelectric film. More specifically, it is not sufficient to resolve the decline in d31 properties caused by the fact that the displacement created by expansion and contraction of the piezoelectric film along the film surface direction is restricted by the substrate constraint.